A conventional device of this kind is disclosed, for example, in U.S. Pat. No. 4,858,572. This device includes a cam shaft rotatably assembled with a cylinder head of an engine; a rotational transmitting member mounted around the peripheral surface of the cam shaft so as to rotate relative thereto within a predetermined range for transmitting a rotational power from a crank pulley; a plurality of vanes provided on the cam shaft or the rotational transmitting member; fluid chambers formed between the cam shaft and the rotational transmitting member and separated into advancing chambers and delaying chambers by the vanes; a first fluid passage for feeding and discharging a fluid to and from the advancing chambers; a second fluid passage for feeding and discharging a fluid to and from the delaying chambers; a retracting bore formed in the rotational transmitting member and accommodating a locking pin and a spring to act on the locking pin; a receiving bore formed on the cam shaft; and a third fluid passage for feeding to the receiving bore.
In the above device, both the retracting bore and the receiving bore are formed in the radial reduction of the cam shaft. There is a stop member which is located at the outer end of the retracting bore. The stop member is tightly pressed into the retracting bore to support one end of the spring. When the stop member is pressed, the stop member shaves the inside surface of the retracting bore such that the shaving grounds are disposed between the outer surface of the locking pin and the inner surface of the retracting bore. Thus, the locking pin is not able to slide smoothly. The problem is avoided by shaving the inside surface of the retracting bore, when the pressed area of the stop member decreases. However, the strength of the press decreases such that the stop member is dropped out from the retracting bore.
On the other hand, there is another type of the device whose retracting bore includes a ring groove on the inner surface thereof so as to engage with a snap ring. The snap ring supports one end of the spring. However, in the above structure, to make the ring groove is very difficult and to engage the snap ring with the ring groove is very difficult. Thereby, the manufacturing cost of the device becomes expensive.